PURPOSE: To ensure a sufficiently high charging efficiency for a high-speed operation of an engine with a suction device of a simple structure by connecting openings of suction ports to an inner wall of a cylindrical valve tangentially for generating strong swirls.

CONSTITUTION: A pair of suction ports 11 and 12 are tangentially opened on an inner wall 10 of a valve chamber 9, and their extensions are constructed not to imply the axial line of a suction valve 4. In this construction, the air sucked into a valve chamber 9 from suction ports 11 and 12 by the opening of the suction valve 4 is swirled along the inner wall 10 of the valve chamber 9 as an arrow W shows for generating strong swirls in a combustion chamber via the suction valve 4.